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From Otis Gospodnetic <>
Subject Re: Push/pull model between leader and replica in one shard
Date Tue, 16 Apr 2013 22:29:32 GMT

Replication when everything is working well is push:
* request comes to any node, ideally leader
* doc is indexed on leader
* doc is copied to replicas

If replica falls too far behind (not exactly sure what the "too far"
threshold is), it uses pull to replicate the whole index from leader.
Mark can answer the part about where tlog gets replayed to catch up on
docs that were missed while big index replication pull was happening.

This is a good thread to read on this topic:

Solr & ElasticSearch Support

On Tue, Apr 16, 2013 at 1:36 AM, SuoNayi <> wrote:
> Hi, can someone explain more details about what model is used to sync docs between the
lead and
> replica in the shard?
> The model can be push or pull.Supposing I have only one shard that has 1 leader and 2
> when the leader receives a update request, does it will scatter the request to each available
and active
> replica at first and then processes the request locally at last?In this case if the replicas
are able to catch
> up with the leader can I think this is a push model that the leader pushes updates to
it's replicas?
> What happens if a replica is behind the leader?Will the replica pull docs from the leader
and keep
> a track of the coming updates from the lead in a log(called tlog)?If so when it complete
pulling docs
> it will replay updates in the tlog at last?
> regards

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